Thermoelectric coolers are often referred to as TEC's or Peltier devices. These devices are actually heat pumps which operate on physical principles established over a century ago by Peltier.
In a TEC, semiconductor materials with dissimilar characteristics are connected electrically in series and thermally in parallel, so that two junctions are created. The semiconductor materials are N and P-type, and are so named because either they have more electrons than necessary to complete a perfect molecular lattice structure (N-type) or not enough electrons to complete a lattice structure (P-type). The extra electrons in the N-type material and the holes left in the P-type material are called "carriers" and they are the agents that move the heat energy from the cold to the hot junction.
Heat absorbed at the cold junction is pumped to the hot junction at a rate proportional to carrier current passing through the circuit and the number of couples.
In a typical TEC, alternatively columns of these N-type and P-type semiconductor materials have their ends connected in a serpentine fashion by electrical conductors. These electrical conductors typically are metallizations formed on insulating (ceramic) plates.
With the application of dc to the TEC, heat is absorbed on the cold side ceramic, passes through the semiconductor material, and is dissipated at the hot side ceramic.
A heat sink must be attached to the hot side ceramic for dissipating the heat from the TEC to the surrounding environment. Without a heat sink, the TEC would overheat and fail within seconds.
Thus, the efficiency of a TEC is a function of the material properties of the semiconductor modules and their operating junction temperatures. The electrical losses and the efficiency of the heat sink are all variables tha effectively control the cost and economic feasibility of a TEC.
Accordingly, this invention is concerned with the heat sink.
In the past, heat sinks have been manufactured using an extrusion process to form a plate having fins extending from one surface of the plate. The problem with the extrusion method is the limited number of fins which can be extruded, due to the limitations of the process. The limited number of fins on the plate thus reduces the cooling area available. The result is a decrease in the efficiency of the heat sink.
In an effort to increase the efficiency of the heat sink, fin retaining posts have been extruded from the front surface of a plate and fins are inserted between the posts. A grease joint is provided between the fins and the plate to increase thermal exchange between the two elements. The fins are secured in thermal contact with the plate by a rod inserted between the retaining posts and the fins. Those persons desiring more information concerning the details of this structure are referred to U.S. Pat. No. 4,734,139, issued Mar. 29, 1988.
Disadvantages of the above described heat sink structure lie in the complexity of the device which increases its manufacturing cost, and the cost of assembly attending the formation of the grease joints and the placement of the fin retaining rods.